The spine can be considered to be a series of movable segments made up of vertebrae and discs. Due to trauma, disease, and/or aging, the spine may be subject to degeneration. This degeneration may destabilize the spine and cause pain and/or nerve damage. Medical procedures are often required to either ease back pain, repair damage, or to prevent future damage.
One procedure that is often used to treat back pain or spinal damage is spinal fusion. Spinal fusion is a surgical technique used to combine two or more adjacent vertebrae. Supplemental bone tissue is used in conjunction with the patient's natural osteoblastic processes in a spinal fusion procedure. Spinal fusion is used primarily to eliminate back pain caused by the motion of the damaged vertebrae by immobilizing adjacent vertebrae. Conditions for which spinal fusion might be done include degenerative disc disease, treatment of a spinal tumor, a vertebral fracture, scoliosis, degeneration of the disc, spondylolisthesis, or any other condition that causes instability of the spine.
One problem with prior art spinal fusion techniques relates to device migration. For example, prior to complete bone fusion, a fusion device may migrate from the desired position. In examples where bone screws are used, the insertion and tightening of the bone screws tends to cause device migration. Another problem with typical prior art fusion techniques is that fusion devices, or associated plates or fasteners, protrude excessively from the spine, causing discomfort, damage, or danger to surrounding vascular or neurological tissues. A further problem with prior art fusion techniques also involves trajectories of screws that are used in the fusion process.
Yet another problem with the prior art fusion techniques is the difficulty with placing supplemental fixation (i.e., plates and screws) due to gross anatomy constraints, surgical approach, vasculature and neurologic tissues and structures, and variable bone quality of the vertebrae.
There is therefore a need for spinal fusion devices and related spinal fusion procedures that adequately treats degenerative disc disease and other spinal conditions, while providing improvements over the prior art.